Systems and methods for measurement of electrical channel loss

ABSTRACT

In accordance with embodiments of the present disclosure, a method for characterizing electrical characteristics of a communication channel between a transmitter of a first information handling resource and a receiver of a second information handling resource may include receiving a test signal at the receiver from the transmitter during an in-situ characterization mode of the second information handling resource, converting the test signal into a discrete-time digital signal representing the test signal, generating a discrete-time finite difference function comprising a first derivative of the discrete-time digital signal, transforming the discrete-time finite difference function into a frequency-domain transform of the discrete-time finite difference function.

The present patent application is a continuation of a previously filedpatent application, U.S. patent application Ser. No. 14/052,050, filedOct. 11, 2013, the entirety of which is hereby incorporated byreference.

TECHNICAL FIELD

The present disclosure relates in general to information handlingsystems, and more particularly to measurement of electrical channel lossin communications paths in information handling systems.

BACKGROUND

As the value and use of information continues to increase, individualsand businesses seek additional ways to process and store information.One option available to users is information handling systems. Aninformation handling system generally processes, compiles, stores,and/or communicates information or data for business, personal, or otherpurposes thereby allowing users to take advantage of the value of theinformation. Because technology and information handling needs andrequirements vary between different users or applications, informationhandling systems may also vary regarding what information is handled,how the information is handled, how much information is processed,stored, or communicated, and how quickly and efficiently the informationmay be processed, stored, or communicated. The variations in informationhandling systems allow for information handling systems to be general orconfigured for a specific user or specific use such as financialtransaction processing, airline reservations, enterprise data storage,or global communications. In addition, information handling systems mayinclude a variety of hardware and software components that may beconfigured to process, store, and communicate information and mayinclude one or more computer systems, data storage systems, andnetworking systems.

Various components of information handling systems often employhigh-speed communication. As communication speeds increase, electricalloss in a communications channel between a transmitting component and areceiving component of the information handling system may becomeincreasingly problematic, and accordingly, it is desirable formanufacturers of information handling systems and their variousinformation handling resources to measure and characterize suchelectrical loss, which may vary according to process differences,manufacturer differences, and other differences. However, many existingapproaches applied to measure electrical loss of a communicationschannel do not effectively isolate the loss and other electricalcharacteristics of the channel from loss caused by the transmittingcomponent and the receiving component (e.g., equalization filteringmechanisms of a receiving block).

SUMMARY

In accordance with the teachings of the present disclosure, thedisadvantages and problems associated with electrical channel lossmeasurement have been reduced or eliminated.

In accordance with embodiments of the present disclosure, an informationhandling system may include a processor, a first information handlingresource communicatively coupled to the processor, and a secondinformation handling resource communicatively coupled to the processorand the first information handling resource, and a baseboard managementcontroller communicatively coupled to the second information handlingresource. The second information handling resource having a receiverconfigured to receive a test signal from a transmitter of the firstinformation handling system resource during an in-situ characterizationmode of the second information handling resource, convert the testsignal into a discrete-time digital signal representing the test signal,and generate a discrete-time finite difference function comprising afirst derivative of the discrete-time digital signal. The baseboardmanagement controller may be communicatively coupled to the secondinformation handling resource and configured to transform thediscrete-time finite difference function into a frequency-domaintransform of the discrete-time finite difference function.

In accordance with these and other embodiments of the presentdisclosure, a method for characterizing electrical characteristics of acommunication channel between a transmitter of a first informationhandling resource and a receiver of a second information handlingresource may include receiving a test signal at the receiver from thetransmitter during an in-situ characterization mode of the secondinformation handling resource, converting the test signal into adiscrete-time digital signal representing the test signal, generating adiscrete-time finite difference function comprising a first derivativeof the discrete-time digital signal, transforming the discrete-timefinite difference function into a frequency-domain transform of thediscrete-time finite difference function.

In accordance with these and other embodiments of the presentdisclosure, an article of manufacture may include non-transitorycomputer-readable media and computer-executable instructions carried onthe non-transitory computer-readable media, the instructions readable byone or more processors. The instructions, when read and executed, maycause the one or more processors to characterize electricalcharacteristics of a communication channel between a transmitter of afirst information handling resource and a receiver of a secondinformation handling resource, wherein the instructions for causing theone or more processors to characterize the electrical characteristicscomprise instructions for causing the processor to receive a test signalat the receiver from the transmitter during an in-situ characterizationmode of the second information handling resource, convert the testsignal into a discrete-time digital signal representing the test signal,generate a discrete-time finite difference function comprising a firstderivative of the discrete-time digital signal, and transform thediscrete-time finite difference function into a frequency-domaintransform of the discrete-time finite difference function.

Technical advantages of the present disclosure may be readily apparentto one skilled in the art from the figures, description and claimsincluded herein. The objects and advantages of the embodiments will berealized and achieved at least by the elements, features, andcombinations particularly pointed out in the claims.

It is to be understood that both the foregoing general description andthe following detailed description are examples and explanatory and arenot restrictive of the claims set forth in this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present embodiments and advantagesthereof may be acquired by referring to the following description takenin conjunction with the accompanying drawings, in which like referencenumbers indicate like features, and wherein:

FIG. 1 illustrates a block diagram of an example information handlingsystem, in accordance with embodiments of the present disclosure;

FIG. 2 illustrates a block diagram of an example receiver, in accordancewith embodiments of the present disclosure; and

FIG. 3 illustrates a flow chart of an example method for measuringelectrical channel loss, in accordance with embodiments of the presentdisclosure.

DETAILED DESCRIPTION

Preferred embodiments and their advantages are best understood byreference to FIGS. 1-3, wherein like numbers are used to indicate likeand corresponding parts.

For the purposes of this disclosure, an information handling system mayinclude any instrumentality or aggregate of instrumentalities operableto compute, classify, process, transmit, receive, retrieve, originate,switch, store, display, manifest, detect, record, reproduce, handle, orutilize any form of information, intelligence, or data for business,scientific, control, entertainment, or other purposes. For example, aninformation handling system may be a personal computer, a personal dataassistant (PDA), a consumer electronic device, a network storage device,or any other suitable device and may vary in size, shape, performance,functionality, and price. The information handling system may includememory, one or more processing resources such as a central processingunit (CPU) or hardware or software control logic. Additional componentsor the information handling system may include one or more storagedevices, one or more communications ports for communicating withexternal devices as well as various input and output (I/O) devices, suchas a keyboard, a mouse, and a video display. The information handlingsystem may also include one or more buses operable to transmitcommunication between the various hardware components.

For the purposes of this disclosure, computer-readable media may includeany instrumentality or aggregation of instrumentalities that may retaindata and/or instructions for a period of time. Computer-readable mediamay include, without limitation, storage media such as a direct accessstorage device (e.g., a hard disk drive or floppy disk), a sequentialaccess storage device (e.g., a tape disk drive), compact disk, CD-ROM,DVD, random access memory (RAM), read-only memory (ROM), electricallyerasable programmable read-only memory (EEPROM), and/or flash memory; aswell as communications media such as wires, optical fibers, microwaves,radio waves, and other electromagnetic and/or optical carriers; and/orany combination of the foregoing.

For the purposes of this disclosure, information handling resources maybroadly refer to any component system, device or apparatus of aninformation handling system, including without limitation processors,service processors, basic input/output systems (BIOSs), busses,memories, I/O devices and/or interfaces, storage resources, networkinterfaces, motherboards, and/or any other components and/or elements ofan information handling system.

FIG. 1 illustrates a block diagram of an example information handlingsystem 102, in accordance with embodiments of the present disclosure. Insome embodiments, information handling system 102 may be a server. Inother embodiments, information handling system 102 may be a personalcomputer (e.g., a desktop computer or a portable computer). As depictedin FIG. 1, information handling system 102 may include a processor 103,a memory 104 communicatively coupled to processor 103, one or moreinformation handling resources 106 communicatively coupled to processor103 via a bus 108, and a baseboard management controller 114.

Processor 103 may include any system, device, or apparatus configured tointerpret and/or execute program instructions and/or process data, andmay include, without limitation, a microprocessor, microcontroller,digital signal processor (DSP), application specific integrated circuit(ASIC), or any other digital or analog circuitry configured to interpretand/or execute program instructions and/or process data. In someembodiments, processor 103 may interpret and/or execute programinstructions and/or process data stored in memory 104 and/or anothercomponent of information handling system 102.

Memory 104 may be communicatively coupled to processor 103 and mayinclude any system, device, or apparatus configured to retain programinstructions and/or data for a period of time (e.g., computer-readablemedia). Memory 104 may include RAM, EEPROM, a PCMCIA card, flash memory,magnetic storage, opto-magnetic storage, or any suitable selectionand/or array of volatile or non-volatile memory that retains data afterpower to information handling system 102 is turned off.

An information handling resource 106 may include any component system,device or apparatus of information handling system 102 that maycommunicate with processor 103, memory 104, and/or one or more otherinformation handling resources via one or more busses 108. For example,an information handling resource may include service processors, BIOSs,an I/O device, a storage resource, a network interface, or any othersuitable component.

As shown in FIG. 1, one or more information handling resources 106 mayinclude a transmitter 110. A transmitter 110 may comprise any system,device, or apparatus configured to transmit signals to one or morecorresponding receivers 111 of other information handling resources 106via link 112.

Also as shown in FIG. 1, one or more information handling resources 106may include a receiver 111. A receiver 111 may comprise any system,device, or apparatus configured to receive signals from one or morecorresponding transmitters 110 of other information handling resources106 via link 112. In some embodiments, as further described in referenceto FIGS. 2 and 3 below, a receiver 111 may include structure andfunctionality for measurement of electrical channel loss betweentransmitter 110 and receiver 111.

As shown in FIG. 1, information handling resources 106 may becommunicatively coupled via a link 112. Link 112 may comprise anysystem, device, or apparatus configured to transfer data betweeninformation handling resources 106, and may include a point-to-pointconnection.

Baseboard management controller 114 may be coupled to bus 108 and/orreceiver 111 and may comprise a specialized microcontroller which may beembedded on a motherboard of information handling system 114 and coupledto and embedded on the motherboard of information handling system 102.Baseboard management controller 114 may manage an interface betweensystem management software (e.g., which may interface with baseboardmanagement controller 114 via a management network external toinformation handling system 102) and information handling resources ofinformation handling system 102. For example, different types of sensorsbuilt into information handling system 102 may report to baseboardmanagement controller 114 on parameters such as temperature, cooling fanspeeds, power status, operating system status, etc. Baseboard managementcontroller 114 may monitor the sensors and may send alerts to a systemadministrator via the management network if any of the parameters do notstay within preset limits, indicating a potential failure of informationhandling system 102. The administrator can also remotely communicatewith baseboard management controller 114 to take some corrective actionsuch as resetting or power cycling information handling system 102 inorder to cause a stalled operating system to execute again. In addition,as described in greater detail below with respect to FIGS. 2 and 3,baseboard management controller 114 may act in concert with receiver 111to measure electrical channel loss between transmitter 110 and receiver111.

FIG. 2 illustrates a block diagram of an example receiver 111, inaccordance with embodiments of the present disclosure. As shown in FIG.2, receiver 111 may comprise a multiplexer 202, traditional receivercircuitry 204, analog-to-digital converter 206, linear differentiator208, and register 210. Multiplexer 202 may comprise any system, deviceor apparatus configured to receive a signal from transmitter 110 vialink 112 and based on a select signal received from baseboard managementcontroller 114, operate in one of a default mode and a BMC-only mode. Inthe default mode, receiver operates in a normal training mode, andparameters calculated in an in-situ characterization mode (as describedin greater detail below) may be used to assist in such training. In theBMC-only mode, which may take place for example if receiver 111 is notable successfully complete a training mode and/or during a manufacturingtest, the signal from channel 112 may be received by analog-to-digitalconverter 206, processed by linear differentiator 208, and stored inregister 210 as a result of in-situ characterization measurement ofchannel 112, wherein such measurement may be read by baseboardmanagement controller 114 and further processed by baseboard managementcontroller 114 and/or utilized by a user for design and/or debuggingpurposes.

Receiver circuitry 204 may comprise standard receiver circuitryconfigured to process an incoming signal for further processing by thereceiving information handling resource 106, as is known in the art.

Analog-to-digital converter 206 may comprise any system, device, orapparatus configured to convert a continuous physical quantity (i.e. avoltage representing the signal received by receiver 111) to a digitalnumber that represents the quantity's amplitude.

Linear differentiator 208 may comprise any system, device, or apparatusconfigured such that the output of linear differentiator 208 isapproximately directly proportional to the rate of change (the timederivative) of its input.

Register 210 may comprise any system, device, or apparatus configured tostore output signals generated by linear differentiator 208 (e.g., acomputer-readable medium).

As described in greater detail below with respect to FIG. 3, inoperation, receiver 111 and baseboard management controller 114 may workin concert during an in-situ characterization mode to characterizeelectrical channel loss of the channel between transmitter 110 andreceiver 111.

FIG. 3 illustrates a flow chart of an example method 300 for measuringelectrical channel loss, in accordance with embodiments of the presentdisclosure. Method 300 may operate when receiver 111 is placed in anin-situ characterization mode (e.g., when baseboard managementcontroller 114 communicates a select signal to multiplexer 202 such thatan input signal of receiver 111 is communicated to analog-to-digitalconverter 206). According to one embodiment, method 300 may begin atstep 302. As noted above, teachings of the present disclosure may beimplemented in a variety of configurations of information handlingsystem 102. As such, the preferred initialization point for method 300and the order of the steps comprising method 300 may depend on theimplementation chosen.

At step 302, receiver 111 may receive a test signal from transmitter 110via link 112. In some embodiments, the test signal may comprise a series(e.g., 200 or more) of logic zeroes followed by a series (e.g., 1000 ormore) of logic ones, such that the test signal approximates, in theanalog domain, a unit impulse function. In such embodiments, the ratioof logic ones to logic zeroes may be greater than a predetermined ratio(e.g., five). In addition, in such embodiments, the test signal may beperiodically repeated during in-situ characterization.

At step 304, analog-to-digital converter 206 may convert the test signalinto a discrete-time digital signal representing the test signal. Thus,where the test signal received is given by the function x(t) in thecontinuous time domain, the output of analog-to-digital converter 206may be given by the function x(n) (for N=0, 1, 2, . . . , N−1, N) in thediscrete time domain.

At step 306, linear differentiator 208 may generate a discrete-timefinite difference function comprising a first derivative of thediscrete-time derivative signal. Stated another way, lineardifferentiator 208 may generate for each discrete value of x(n) a finitedifference x′(n) (e.g., generate the derivative of) between the discretevalue of the previous (e.g., n−1) discrete value of x(n) such thatx′(n)=x(n+1)−x(n).

At step 308, the finite difference function x′(n) may be stored inregister 210 and communicated to baseboard management controller 114.

At step 310, baseboard management controller 114 may transform finitedifference function x′(n) to the frequency domain such that adiscrete-time frequency-domain transform X(k) may be given by theequation:

${{X(k)} = {\sum\limits_{n = 0}^{N - 1}\;{x(n)}}},{{{\mathbb{e}}^{{- {{\mathbb{i}}{(\frac{2\;\pi}{N})}}}{kn}}{where}\mspace{14mu} k} = 0},1,2,{{\ldots\mspace{14mu} N} - 1},N$wherein such equation may be used to determine loss at each relevantvalue of frequency. After completion of step 310, method 300 may end.

Although FIG. 3 discloses a particular number of steps to be taken withrespect to method 300, method 300 may be executed with greater or fewersteps than those depicted in FIG. 3. In addition, although FIG. 3discloses a certain order of steps to be taken with respect to method300, the steps comprising method 300 may be completed in any suitableorder.

Method 300 may be implemented using information handling system 102 orany other system operable to implement method 300. In certainembodiments, method 300 may be implemented partially or fully insoftware and/or firmware embodied in computer-readable media.

Methods and systems described herein may provide numerous advantages.For example, the methods and systems may permit a design engineer tocharacterize the impact of material variation between one informationhandling resource vendor to another. As another example, the methods andsystems may permit a design engineer to determine full channel loss(e.g., including integrated circuit, package, and printed circuit board)of an electrical path, rather than merely a link (e.g., link 112)between information handling resources. As an additional example, themethods and systems may permit a design engineer to aggressively designinformation handling systems with high-quality, fast links betweeninformation handling resources and the ability to debug both silicon andoverall system-related issues. As a further example, the methods andsystems may permit a design engineer to determine channel-to-channel andslot-to-slot variation across single and multiple information handlingsystems in a high-volume production environment. As yet another example,the methods and systems may permit a design engineer to understandinformation handling system behavior and interconnect behavior in acomplex interconnect configuration.

Although the present disclosure has been described in detail, it shouldbe understood that various changes, substitutions, and alterations canbe made hereto without departing from the spirit and the scope of thedisclosure as defined by the appended claims.

What is claimed is:
 1. An information handling system comprising: aprocessor; a first information handling resource communicatively coupledto the processor; a second information handling resource communicativelycoupled to the processor and the first information handling resource,the second information handling resource having a receiver configuredto: receive a test signal from a transmitter of the first informationhandling system resource; convert the test signal into a discrete-timedigital signal representing the test signal; and generate adiscrete-time finite difference function comprising a first derivativewith respect to time of the discrete-time digital signal; and abaseboard management controller communicatively coupled to the secondinformation handling resource and configured to transform thediscrete-time finite difference function into a frequency-domaintransform of the discrete-time finite difference function.
 2. Theinformation handling system of claim 1, wherein the test signalapproximates a unit impulse function.
 3. The information handling systemof claim 1, wherein the test signal comprises a digital string of logiczeroes followed by a digital string of logic ones.
 4. The informationhandling system of claim 3, wherein a ratio of the number of logic onesto the number of logic zeroes is greater than or equal to five.
 5. Amethod for characterizing electrical characteristics of a communicationchannel between a transmitter of a first information handling resourceand a receiver of a second information handling resource comprising:receiving a test signal at the receiver from the transmitter; convertingthe test signal into a discrete-time digital signal representing thetest signal; generating a discrete-time finite difference functioncomprising a first derivative with respect to time of the discrete-timedigital signal; and transforming the discrete-time finite differencefunction into a frequency-domain transform of the discrete-time finitedifference function.
 6. The method of claim 5, wherein the test signalapproximates a unit impulse function.
 7. The method of claim 5, whereinthe test signal comprises a digital string of logic zeroes followed by adigital string of logic ones.
 8. The method of claim 7, wherein a ratioof the number of logic ones to the number of logic zeroes is greaterthan or equal to five.
 9. An article of manufacture comprising:non-transitory computer-readable media; and computer-executableinstructions carried on the non-transitory computer-readable media, theinstructions readable by one or more processors, the instructions, whenread and executed, for causing the one or more processors tocharacterize electrical characteristics of a communication channelbetween a transmitter of a first information handling resource and areceiver of a second information handling resource, wherein theinstructions for causing the one or more processors to characterize theelectrical characteristics comprise instructions for causing theprocessor to: receive a test signal at the receiver from thetransmitter; convert the test signal into a discrete-time digital signalrepresenting the test signal; generate a discrete-time finite differencefunction comprising a first derivative with respect to time of thediscrete-time digital signal; and transform the discrete-time finitedifference function into a frequency-domain transform of thediscrete-time finite difference function.
 10. The article of claim 9,wherein the test signal approximates a unit impulse function.
 11. Thearticle of claim 9, wherein the test signal comprises a digital stringof logic zeroes followed by a digital string of logic ones.
 12. Thearticle of claim 11, wherein a ratio of the number of logic ones to thenumber of logic zeroes is greater than or equal to five.